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arXiv 1601.02091astro-ph.GAastro-ph.CO
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COSMOS中PDKEEPAAA宿主星系质量函数:AGN反馈对星系质量猝灭负责吗?

AGN host galaxy mass function in COSMOS: is AGN feedback responsible for the mass-quenching of galaxies?

A. Bongiorno, A. Schulze, A. Merloni, G. Zamorani, O. Ilbert, F. La Franca, Y. Peng, E. Piconcelli, V. Mainieri, J. D. Silverman, M. Brusa, F. Fiore, M. Salvato, N. Scoville

摘要:

我们通过测量宿主星系的恒星质量函数(HGMF)和特定的吸积率,即,λ_SAR,分布函数(SARDF),z~2.5与~1000 X射线从XMM-COSMOS选择AGN。利用极大似然方法,我们联合拟合恒星质量函数和比吸积率分布函数,并以X射线光度函数作为附加约束。我们的最佳拟合模型将SARDF描述为具有质量依赖但与红移无关的双幂律破缺,其低Lambda_SAR斜率随着红移的增加而增加,同时归一化增加。这意味着,对于一个给定的恒星质量,较高的lambda_SAR对象有一个峰值,在其空间密度在较早的时代相比,较低的lambda_SAR的,以下和模仿众所周知的AGN宇宙缩小AGN光度函数中观察到的。活动星系的质量函数用Schechter函数来描述,它具有几乎恒定的Mstar* 和低的质量斜率α,α随红移而变化。与恒星质量函数相比,HGMF具有相似的形状,并且在log((Mstar/Msun)~11.5范围内,活动星系核宿主星系与恒星形成星系的比例基本保持不变(~10%)。最后,不同光度和比吸积率子类的活动星系核HGMF与Peng等人(2010)对“瞬态”群体(即处于质量猝灭过程中的星系)的唯象模型预测的比较表明,低光度活动星系核似乎不能对猝灭做出显着贡献,至少在高质量时,即Mstar>10^(10.7)Msun,来自活动星系核的反馈(log(Lbol)>~46 [erg/s])可能是导致宿主星系恒星形成猝灭的原因。

英文摘要:

We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate i.e., lambda_SAR, distribution function (SARDF) up to z~2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best fit model characterizes the SARDF as a double power-law with mass dependent but redshift independent break whose low lambda_SAR slope flattens with increasing redshift while the normalization increases. This implies that, for a given stellar mass, higher lambda_SAR objects have a peak in their space density at earlier epoch compared to the lower lambda_SAR ones, following and mimicking the well known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with a almost constant Mstar* and a low mass slope alpha that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that, up to log((Mstar/Msun)~11.5 the ratio of AGN host galaxies to star forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate sub-classes with the phenomenological model prediction by Peng et al. (2010) for the "transient" population, i.e. galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, i.e. Mstar>10^(10.7) Msun , feedback from luminous AGN (log(Lbol)>~46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

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